Device for Detecting the Condition of a Tire on a Wheel

ABSTRACT

A device for detecting the condition of a tire ( 2 ) on a wheel ( 3 ) of a vehicle ( 1 ), having at least one sensor ( 4 ) which ascertains condition data of the tire ( 2 ) and outputs them to a receiving unit of the vehicle ( 1 ), is propose in which at least one sensor ( 4 ) in the vehicle is provided, which ascertains values representing a distance (D 1 , D 1 ′, D 2 , D 3 , D 3′ ) to at least one target ( 5, 6, 7 ) affixed to the tire ( 2 ) and outputs them to an evaluation device ( 8 ), which from that ascertains condition data of the tire ( 2 ) (FIG.  1 ).

PRIOR ART

The invention relates to a device for detecting the condition of a tireon a wheel, as defined in more detail by the preamble to claim 1.

In the industry, devices for ascertaining a tire condition are knownthat operate on various principles; as a rule, these devices areconceived for ascertaining the correct air pressure of the tire andascertain condition data of the tire by means of sensors and outputthese data to a receiving unit of the vehicle and/or calculate orestimate condition data of the tire by means of control/regulatingsystems of the vehicle, such as an anti-lock brake system, an electronicstability program, or an electrohydraulic brake system.

Tire condition detection with systems on the vehicle that make use ofrpm sensor information and vehicle information, for instance fromsystems connected to an engine/transmission controller,disadvantageously do not provide actual condition values of the tire butonly indirect calculations and estimates. Besides the attendantinaccuracy, ascertaining tire condition in this way is also slow becauseof the system and, depending on the driving dynamics, requires a longerdistance to be covered by the vehicle.

Tire condition detection using a sensor which outputs the ascertainedvalues in wireless fashion to a receiving unit of the vehicle isdescribed for instance in European Patent Disclosure EP 0 746 475 B1. Atransponder is used here for detecting, storing in memory and sendingtire condition parameter data for a vehicle tire; the transponder isconnected to an energy supply and an antenna and in response to a querysignal from a querying means on the vehicle outputs tire conditionparameter data, particularly the air pressure and the temperature, tothe querying means.

From German Patent Disclosure DE 199 40 086 A1, a method for identifyingtires, especially aircraft tires, by means of integrated transpondersand documentation of the usage data of the tire, including pressure andtemperatures in the transponder, is known.

Such solutions to the problem, in which a battery-operated sensor, forinstance, which is located on or in the tire forwards information, suchas the internal tire pressure, either temperature-corrected or with anadditional piece of temperature information, to a separate receivingunit of the vehicle, however, are disadvantageous in the sense thatthese sensors must always be recalibrated every time a tire is changed.

It is also known from the industry to provide a tire with magneticelements and to detect a change in magnetic field upon rotation of thewheel by way of a suitable rpm sensor in the vicinity of the side of thetire. In this way, torsion of the side of the tire can be recognized.

However, in such a method it is disadvantageous that only special tireswith the appropriate magnetic shafts may be used, and the amount ofcondition data of the tire that can thus be attained is low.

It is the object of the present invention to create a device fordetecting the condition of a tire on a wheel of a vehicle with which thegreatest possible amount of condition data of the tire can beascertained reliably and quickly at little engineering effort orexpense.

According to the invention, this is object is attained in a device ofthe type defined at the outset, having the characteristics of the bodyof claim 1.

ADVANTAGES OF THE INVENTION

A device for detecting the condition of a tire on a wheel of a vehiclehaving at least one sensor, in an advantageous embodiment according towhich at least one sensor in the vehicle is provided, which ascertainsvalues representing a distance to at least one target affixed to thetire and outputs them to an evaluation device, which from thatascertains condition data of the tire, has the advantage first thatlocating the at least one sensor on the vehicle enables simple energysupply and data transmission.

Utilizing the distance information between the at least one sensor and atarget affixed to the tire furthermore makes it possible, very quickly,to make reliable statements about many condition data of the tire.

For instance, monitoring the distance between the target on a side ofthe tire in the region of where the tire contacts the road surface andthe sensor makes it possible to quickly make statements about a pressurecondition or tire filling condition and a load condition of the tire,since shortening of this critical distance indicates either underfillingof the tire or a heavy load on the tire.

Moreover, the distance measurement makes it possible to make statementsabout the kind of load on the tire, such as a torsional load, and abouta tire surface condition, since bulges, dents, fragmentation, andpossibly nails driven into the tire are detectable via a distancemeasurement.

Depending on the sensor resolution, the condition of the tire tread canalso be ascertained with the device of the invention, that is, thepresence of a rated tread height or a reduced tread height.

With the use of distance information according to the invention, it isalso possible to distinguish between a summer tire condition and awinter tire condition; to that end, the distance information canadvantageously be combined by the evaluation device with a detection ofthe coefficient of friction.

By means of a periodic measurement signal, an imbalance condition of thetire that might be present can also be ascertained.

Besides monitoring the condition of the tire in the narrower sense,monitoring of rotating components that are connected to the tire isadvantageously also possible, so that with the device of the invention,a rim condition can also be monitored for rim damage.

In an advantageous embodiment of the device of the invention, the atleast one sensor may be designed such that it ascertains distance valuesand/or speed values of the at least one target.

With the speed values of the wheels, additional calculations may bemade, such as calculating the wheel moments.

The at least one sensor may be disposed in static fashion on the vehiclechassis, for instance fixedly on an axle of the vehicle. However, thesensor may also be located on some component, such as a strut, that isdynamically connected to the vehicle chassis, with the advantage that adynamic measurement can be performed in which dynamic changes in thetravel state, such as acceleration, deceleration and cornering, can betracked based on the tire deformation.

In a preferred embodiment of the invention, a first target is affixed toa side or rubber sidewall of the tire; the distance to such a target ishighly conclusive, especially in ascertaining the filling condition ofthe tire and the load condition on the tire.

Alternatively or in addition, targets may also be affixed in the regionof the heel zone or in the region of the shoulder zone at the transitionto the running face of the tire; the latter makes it possible to monitorthe width of the tire tread.

If a rotating reference measurement target is affixed as a furthertarget to the wheel, then advantageously simple self-calibration of theat least one sensor for detecting the condition of a tire is possible.One such reference measurement target may for instance be a region of abead of the rim.

The conclusiveness of a piece of condition information pertaining of thetire can be further enhanced by providing that a further target is atravel surface, and the height of the sensor compared to the travelsurface is ascertained as the distance.

For detecting the distance to the at least one target, the sensor canoperate by various known measurement principles; in particular, anelectromagnetic sensor, such as a radar sensor, which furthermoreascertains a speed component of the detected measurement range, isadvantageous. However, the sensor may also be embodied as an opticalsensor, in particular a lidar sensor or a picture-taking device, or asan acoustic sensor, such as an ultrasound sensor.

Upon a measurement of distances to a plurality of targets, it may beprovided that these distances are detected simultaneously in apredetermined angular range.

In an advantageous embodiment of the invention, however, eithermechanical pivoting to various angular ranges or electronic switchingmay be provided.

For instance, if a radar sensor is used, the entire distance range canbe scanned with a fixed antenna, or by using a scanning antenna, anangular resolution can be generated via a patch array or mechanicalpivoting.

Optical systems that are based on picture-taking, for instance by meansof video, can be designed in analog form; for detecting various angularranges, the use of mirrors is also conceivable.

The condition data of the tire ascertained with the device of theinvention can be made available by the evaluation device, in anadvantageous embodiment of the invention, to a network withcontrol/regulating systems of the vehicle connected to it.

These control/regulating systems, in the case of a motor vehicle, canact on the vehicle drive and transmission or on individual equipmentcharacteristics or safety and information modules. Examples of suchcontrol/regulating systems are an anti-lock brake system, anelectrohydraulic brake system, which is a combination of an electronicand a hydraulic brake, traction control, an electronic stabilizationprogram, automatic tire pressure monitoring with automatic filling,triggering of an axle air shock absorber, electronic shock absorbercontrol, light regulation, illumination width regulation, andvehicle-to-vehicle communications or vehicle-to-control-centercommunications, with which remote diagnosis can be made in the case ofrepair or a breakdown.

To indicate to the driver and/or a maintenance worker that there is adeviation in a tire condition from a rated condition and this deviationrequires handling by the driver or maintenance worker, it is expedientif the evaluation device outputs a corresponding signal to an opticaland/or acoustical and/or haptic display device of the vehicle.

The device of the invention can also cooperate with a memory andreceiver device, known per se, in which by means of transpondertechnology, for instance, data are forwarded from a transmitter in thetire to a receiver in the vehicle. In this way, tire-specific data,which relate for instance to the make, the manufacture, and theallowable maximum speed of the effected tire, or also additionalpressure and temperature values, can be forwarded.

From a memory device of the tire, data ascertained over the life of thetire can be called up; thus even after a tire has been changed thesedata are available and provide information which is undetectable via apurely in-vehicle ascertainment of the tire condition.

Along with the condition data ascertained by the distance measurementaccording to the invention, information pertaining to the tire can thusbe comprehensively obtained, information that can be made available tothe network of control/regulating systems of the vehicle for the sake ofa situation-optimized mode of operation of the vehicle.

Although the device of the invention proves to be highly advantageousparticularly in the case of a motor vehicle, it is not limited to motorvehicles, but can be used in all wheeled means of transportation.Particularly for aircraft, in which for safety reasons reliable tirediagnosis is of great significance, a device for detecting the conditionof a tire according to the invention can be advantageous.

Further advantages and advantageous features of the subject of theinvention can be learned from the description, drawings and claims.

DRAWINGS

One exemplary embodiment of a device according to the invention fordetecting the condition of a tire, with two options for the location ofsensors, is shown schematically and in simplified form in the drawingsand will be described in further detail in the ensuing description.Shown are:

FIG. 1, in a simplified cross section, a detail of a wheel suspension ofa motor vehicle, where a device according to the invention for detectingthe condition of a tire is provided on the wheel shown of the motorvehicle;

FIG. 2, two possible mounting positions of a sensor of the deviceaccording to the invention in the case of a wheel suspension of avehicle;

FIG. 3, a graph that shows the relationship of signal amplitudes to adistance between a sensor of the device of the invention and a detectedtarget on the tire; and

FIG. 4, a flow chart of a method for detecting the condition of a tireusing the device of the invention.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

In FIG. 1, in a motor vehicle 1, a device for detecting the condition ofa tire 2 on a wheel 3 of the motor vehicle 1 is shown, with a sensor 4provided on the vehicle, which sensor, to detect a condition or specificcondition data of the tire 2, ascertains at least one distance to atarget affixed to the tire 2 and outputs it to an evaluation device 8.

The sensor 4, which in the present example is embodied as a radarsensor, measures a distance to a first target 5, affixed to a side ofthe tire 2; reference numeral D1 represents a distance for a definedrated condition of the tire 2, and reference numeral D1′ represents ashortened distance, for instance in the event of an underpressurecondition of the tire 2 and of a deformed tire contour shown in dashedlines.

A second distance D2 ascertained by the sensor 4 represents a referencedistance between the sensor 4 and a reference measurement target 6 onthe wheel 3; the reference measurement target 6 in this case is affixedto a bead of a rim 13 of the wheel 3.

The bead of the rim 13 is especially well suited to affixing a referencemeasurement target, since in this region of the rim 13, unless thevehicle has an accident, no changes in form or position are to beexpected.

The height of the sensor 4 relative to the travel surface 7, the latterrepresenting a further target, is also ascertained as a furtherdistance; reference numeral D3 represents a distance in the ratedcondition of the tire 2 and reference numeral D3′ represents a shorteneddistance, in the underpressure condition of the tire 2 represented by adashed-line tire contour.

As can be seen from FIG. 1, the distances D1 and D3 between the sensor 4and the target 5 on the tire 2, and between the sensor 4 and the travelsurface 7 as shown in dashed lines in the case of underfilling of thetire 2, are shortened to the corresponding distances D1′ and D3′,respectively.

From the distance values or the changes in the distance values, theevaluation device 8 ascertains condition data of the tire 2 and makesthem available to a network 9, here embodied as a CAN bus system, withcontrol/regulating systems 10, 11 connected to it and to display devices12 of the motor vehicle 1.

In FIG. 2, two possible locations of the sensor 4 are shown; a firstposition P1 shows the location of the sensor 4 on a componentoscillating dynamically with the wheel 3 and is connected to the vehiclechassis 15, for instance in this case a strut 14. This position P1 ofthe sensor has the advantage that it is located close to the targets andmakes a dynamic measurement possible.

A stationary location of the sensor 4 at a further position P2 is alsoshown; this position may be provided on a rigid axle element of thevehicle chassis 15. From the position P2, objective distancemeasurements of the sensor 4 to the targets 5, 6, 7 are possible.

In FIG. 3, measurement profiles are shown as amplitudes AMP over adistance d; in principle, reference symbol M_D1 represents a measurementprofile that produces the distance D1 between the sensor 4 and thetarget 5 on the side of the tire 2 in the rated condition of the tire 2;M_D1 represents a measurement profile that produces the distance D1′between the sensor 4 and the target 5 in the case of underfilling of thetire 2; M_D3 represents a measurement profile that produces the distanceD3 between the sensor 4 and the travel surface 7 in the rated conditionof the tire 2; and M_D3′ represents a measurement profile that producesthe distance D3′ between the sensor 4 and the travel surface 7 in thecase of underfilling of the tire 2.

The shift in the measurement profile M_D1 to M_D1′ and the measurementprofile M_D3 to M_D3′ here unambiguously indicates tire deformation;from the tire deformation, by means of a suitable algorithm based on adynamic detection of the shift in the measurement profiles, theunderfilled condition of the tire 2 is detectable.

As can be seen from the graph in FIG. 3, the measurement profiles M_D1and M_D3 on the one hand and M_D1′ and M_D3′ on the other together eachform a respective curve with two pronounced maximum values of markedlydifferent magnitude and minimum values in the form of zero points.

In the use in this case of a sensor 4 embodied as a radar sensor, whichascertains both the distance to the measurement target 5 on the tire andto the travel surface 7 and outputs a speed component of the region inquestion of the side of the tire 2 to the evaluation device 8, it ispossible with knowledge of the geometries and a correspondingassociation, as a function of fixed distance cells, to associate thegreater maximum value with the curve of the measurement profile M_D1 andM_D1′ of the measurement of the distance to the measurement target 5 onthe tire 2, and to associate the lesser maximum with the curve of themeasurement profile M_D3 and M_D3′ of the measurement of the distance tothe travel surface 7.

A clear distinction between the measurement profiles or distance spacesis obtained in the present case from the zero points that occur everytime a switchover of the radar sensor 4 to the applicable target ismade.

As can also be learned from the measurement profiles M_D1, M_D1′, M_D3,M_D3′ of FIG. 3, these each have a strong, virtually continuous drop,beginning at a maximum and extending to a lower distance range, whilethe gradient of the measurement profiles to a greater distance range canhave a considerably shallower course, as can be seen particularly fromthe measurement profiles M_D1 and M_D1′. This shows that the steep dropon the left in the curves M_D1, M_D1′, M_D3, M_D3′ represents asensitive measurement parameter that can be used for extrapolation andinterpolation, and toward greater distances d, interference parametersmay possibly occur.

Performing a detection of the condition of the tire 2 can be done, inthe case of the device of the invention, with a method in accordancewith the flow chart shown in FIG. 4.

In the chart shown in FIG. 4, the amplitudes AMP over the distances arefirst plotted in accordance with the measurement profiles of FIG. 3, ina first function F1.

In the next function F2, the maximum and minimum values of themeasurement profiles are determined, and in a function F3, it isinvestigated whether the outcomes or measurement profiles, such as inthe present example the measurement profiles M_D1′ and M_D3′, arecongruent with associated rated values or rated measurement profilesstored in a memory unit, namely in the present case the measurementprofiles M_D1 and M_D3, respectively.

If there is more than one maximum value, an evaluation of the signalsfor the respective maximum values is done in a further function F4; thisis followed in the next function F5 by a comparison of the maximumvalues with rated values or empirical values, which may be static anddynamic values for the rated condition.

Next, in a further function F6 of the flow chart, a dynamic adaptationof the rated values may be done.

In a further function F7, it is checked whether the rated values for thedistance D1 to the measurement target 5 on the side of the tire 2 andthe distance D3 to the travel surface 7 are matched. If such a match isascertained in the distinguishing function F7, then in the next functionF8 it is output that the outcomes or measurement profiles can be used byan algorithm of a control unit of the motor vehicle.

Furnishing the information or results for use by control/regulatingsystems, connected for instance to an on-board electrical system of thevehicle, is done in a further function F10.

If a deviation from the rated values is ascertained in thedistinguishing function F7, then in the next distinguishing function F9,a selection among the values is made with regard to whether they can beused, or whether the signals are not usable further.

If the signals can continue to be used, then for furnishing use a jumpis made to the corresponding function F10. If the deviations are greaterthan a predetermined threshold, and thus are defined as not furtherusable, then in the next function F14 it is output that the signal isnot usable.

Next, in a following function F15, emergency operation of the system isstarted, and this information is output to the function F10 for use ofthe measurement profiles by the network of the vehicle and of theregulator algorithms of the connected control/regulating systems.

If in the function F3 in the investigation of the measurement profilesfor congruence with the rated values a deviation is found which isdefined for a defect in the sensor, for instance if only one maximumvalue is detectable, then an emergency operation evaluation is startedwith a function F11, instead of performing the evaluation of the signalsfor maximum values in the function F4.

In the emergency operation evaluation, it is checked in a distinguishingfunction F12 whether an ascertained deviation of a measurement profilefrom rated values is evaluatable or is implausible. If the ascertaineddeviations are outside a defined plausibility range, then in the nextfunction F13 it is output that a possible sensor defect exists, and ajump is made to function F14, which outputs the fact that the signal isnot usable, whereupon an emergency system operation is started inaccordance with function F15, and this information is output to thefunction F10 for use of the measurement profiles by the connectedregulator algorithms in the vehicle.

If in the emergency operation evaluation in function F12 it isascertained that an existing change or measurement profile deviation isevaluatable, then in a subsequent function F15 the information thatthere is a tire defect can be generated and output to the function F10for use of the information by the control/regulating systems of thevehicle.

Once the information in accordance with the function F10 is madeavailable to different control/regulating systems by way of the on-boardelectrical system of the motor vehicle, this information is read in byone of these systems in a subsequent function F17; for instance, acomparison is made with empirical values or standard values stored inmemory in a database, and the existing information is checked fordeviations.

Depending on the outcome of the processing of the information in thefunction F17, in the next function F18 a reaction by the particularevaluation device or control unit involved takes place.

The latter can, in the case of dynamic measurement by the sensor 4, forinstance, output the information in the next function F19 that dynamicchanges in the travel condition, such as acceleration, deceleration andcornering, exist.

Moreover, in a function F20, the calculation of the wheel moments can bestarted; both the statements about dynamic changes in the travelcondition of the function 19 and the wheel moments of the function 20can be processed in the next function F21, which represents a regulatingalgorithm for adjusting the travel speed. The speed governing is thusbased on qualitative signals and secure information.

The applicable evaluation device or control unit can moreover allocatethe existing information, as condition data of the tire, with a definedcondition and can output this condition as a signal.

In the flow chart of FIG. 4, an imbalanced condition of the tire isshown as condition Z1; a pressure condition of the tire is shown ascondition Z2; a tread condition of the tire is shown as condition Z3; atire surface condition is shown as condition Z4; a summer tire/wintertire condition is shown as condition Z5; an existence of an illegal useof tires or rims is shown as condition Z6; and a rim condition is shownas condition Z7, as examples.

Moreover, in a function F22, as a reaction to the function F18, aself-calibration of the sensor by reference to the rim can be requested.

Depending on the condition output, in the next function F23 provisionsassociated with the applicable condition are initiated, such as anemergency operation program, the activation of optical and/or acousticaland/or haptic warning signals, an automatic speed limitation, a changein the braking characteristic, a change in the engine characteristic, oran adaptation of acceleration conditions to the road surface.

Based on the provisions made, in a further function F24 a selection ofhypotheses and an allocation of the provisions to categories is done;for example, prioritizing of individual provisions can be defined.

Finally, in a function F25, a recursion of the above-described sequencetakes place for a new measurement cycle.

1-15. (canceled)
 16. A device for detecting a condition of a tire on awheel of a vehicle; comprising a receiving unit adapted to be providedin a vehicle; at least one sensor which ascertains condition data of thetire and outputs them to said receiving unit; an evaluation device, saidat least one sensor being adapted to be provided in the vehicle andconfigured to ascertain values representing a distance to at least onetarget element affixed to the tire and output them to said evaluationdevice which from that ascertains condition data of the tire, whereinsaid at least one target element includes a first target adapted to beaffixed to one side of the tire and a further target which is a rotatingreference measurement target on the wheel.
 17. A device as defined inclaim 16, wherein said further target is a travel surface, and a heightof said at least one sensor above the travel surface is ascertained asthe distance.
 18. A device as defined in claim 16, wherein said at leastone sensor is configured to ascertain speed values of said at least onetarget element.
 19. A device as defined in claim 16, wherein saidevaluation unit is configured so that from the values selected from thegroup consisting of a distance values, speed values, and both, saidevaluation unit ascertains variables which are compared with ratedvalues; and further comprising a memory unit which stores the ratedvalues.
 20. A device as defined in claim 19, wherein said evaluationunit is configured so that it ascertains amplitudes of the distance,maximums of which amplitudes are compared with rotated values stored inmemory.
 21. A device as defined in claim 16, wherein said at least onesensor is adapted to be located in static fashion on a vehicle chassis.22. A device as defined in claim 16, wherein said at least one firstsensor is adapted to be located on a component that is connecteddynamically to a vehicle chassis.
 23. A device as defined in claim 22,wherein said at least one sensor is adapted to be located on a strutthat is connected dynamically to a vehicle chassis.
 24. A device asdefined in claim 16, wherein said at least one sensor is a sensorselected from the group consisting of an electromagnetic sensor, anoptical sensor, and an acoustic sensor.
 25. A device as defined in claim24, wherein said electromagnetic sensor is configured as a radar sensor.26. A device as defined in claim 24, wherein said optical sensor is asensor selected from the group consisting of a lidar sensor and apicture-taking device.
 27. A device as defined in claim 24, wherein saidacoustic sensor is configured as an ultrasound sensor.
 28. A device asdefined in claim 16, wherein said at least one sensor is configured toascertain the condition data of the tire selected from the groupconsisting of tire pressure condition, tire load condition, rod, tiretread condition, summer tire condition, winter tire condition, and tireimbalance condition.
 29. A device as defined in claim 16, wherein saidat least one sensor is configured to ascertain condition data of thetire which is a rim condition.
 30. A device as defined in claim 16,wherein said evaluation device is configured so as to make conditiondata of the tire available to an element selected from the groupconsisting of a network having control/regulating systems connected toit, at least one display device of the vehicle, and both.
 31. A deviceas defined in claim 16, wherein the device for detecting a condition ofa tire on a wheel of a vehicle is configured as a device for detecting acondition of a tire on a wheel of a motor vehicle.
 32. A device asdefined in claim 16, wherein the device for detecting a condition of atire on a wheel of a vehicle is configured as a device for detecting acondition of a tire on a wheel of an aircraft.